Does concomitant thyroid disorder lead to worse outcomes in frozen shoulder? - A systematic review.

Background: Frozen shoulder is a common pathology characterized by significant shoulder pain, range of motion limitation and physical disability. There exists a clear association between the prevalence of frozen shoulder and thyroid disease. However, the effects of concomitant thyroid disease on clinical outcomes of frozen shoulder are less well established. This study aims to evaluate if the presence of thyroid disease predisposes to poorer clinical outcomes in patients with frozen shoulder.

Methodology: The study was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and registered with PROSPERO. Two databases (PubMed and Embase) were searched from date of inception to 9 January 2024. Human studies reporting clinical outcomes of patients with concomitant thyroid disorder and frozen shoulder were included. Risk of bias was assessed based on the Quality In Prognosis Studies (QUIPS) tool and quality of evidence was judged based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework in the domains of range of motion, responsiveness to treatment or timeliness of recovery, and multidimensional scoring systems.

Results: Seven studies comprising 167,397 subjects (mean age 52.7 to 58 years, female proportion 67.1%), including 49,314 patients with concomitant thyroid disorder and frozen shoulder were included. Amongst the seven included studies: one study reported improved clinical outcomes in patients with concomitant frozen shoulder and hypothyroidism, one study reported that presence of thyroid disorder led to worse outcomes, while the remaining five studies did not demonstrate evidence of statistically worse outcomes in patients with concomitant thyroid disorder. Based on the GRADE framework, there was no consistent prognostic association between thyroid disorder and frozen shoulder in the domains of range of motion, responsiveness to treatment or timeliness of recovery, and multidimensional scoring systems, and the quality of evidence ranged from 'Very Low' to 'Low'.

Risk of bias assessment: Based on the QUIPS tool, three studies were assessed to have low risk of bias, while four studies were assessed to have moderate risk of bias.

Conclusion: Though there exists an association between the prevalence of frozen shoulder and thyroid disorder, there is no consistent evidence in available literature to suggest that concomitant thyroid disorder predisposes to worse clinical outcomes.